Conventionally, when forming circular stitches with a sewing machine, a circular stitcher having a pin secured to it is attached to the sewing machine by the user. The pin is pierced through a workpiece cloth at a position laterally spaced from the needle drop point. Then, the workpiece cloth is rotated about the pin by the feed dog to form circular stitches in combination with the vertical movement of the needle bar having a sewing needle attached to it.
When forming circular stitches, the user is required to adjust the alignment of the workpiece cloth so that the center of rotation for forming circular stitches is pierced by the pin secured on the circular stitcher attached to the sewing machine. Because the pin is secured to the circular stitcher, precise cloth alignment is difficult and troublesome for the user since the user is required to peek under the workpiece cloth for adjustment in alignment. Consequently, the center of rotation for forming circular stitches is often displaced, resulting in patterns being formed in undesired positions.
A circular stitcher allowing detachable attachment of the pin to the stitcher body is suggested to address such issues.
The circular stitching unit described in JP H04-375 U (related publication 1) is provided with a stopper plate having three stopper holes. A needle base plate provided with a pin is detachably attached to the three stopper holes. The user may selectively attach the needle base plate to one of the three stopper holes of the stopper plate in order to position the pin to the center of the circular stitching.
The circular stitching unit described in related publication 1 allows detachable attachment of the needle base plate to the stopper plate. However, under such configuration, increase in clearance between the stopper hole of the stopper plate and the needle base plate for facilitating attachment/detachment of the needle base plate to/from the stopper plate renders the needle base plate susceptible to rattling, consequently leading to displacement in circular stitch patterns.
As opposed to this, when clearance between the stopper hole of the stopper plate and the needle base plate is reduced to eliminate rattling of the needle base plate caused by the attachment of the needle base plate, attachment/detachment of the needle base plate to/from the stopper hole becomes troublesome.